It is well known to those skilled in the petroleum chemical field that delayed coking process is one of the main technical means for transforming cheap heavy oil into light oil product having high additional value currently, which is important in oil refining industry of the world. The delayed coking process is one of the sources of the main economic benefit in oil refining combined equipments, and even is a heavy oil processing method mainly developed by many countries such as China and the United States. However, the delayed coking process needs a large amount of cooling water, thus inevitably producing a large amount of coke-cooling wastewater. In particular, the coke-cooling wastewater produced in the delayed coking oil refining process, which uses high sulfur heavy oil as raw material, not only contains solid coke breeze and liquid heavy oil, but also contains many sulfides (including inorganic sulfides and organic sulfides), the temperature of which is up to 85-125° C., having already been one of the main pollution sources which compromises the human living environment, and being a difficult problem puzzling people in a long time.
Chinese utility model patent ZL 02216056.6 discloses a closed-cycling process unit for delayed coke-cooling water, which is desired to solve the problem of purifying coke-cooling wastewater. However, such a process unit is proved to have the following defects in practice:
1. Cyclone deoiling separators and air coolers, both of which have multistage structures in series, are needed, so the cost of the process unit is large. Furthermore, hot-water pump for coke-cooling wastewater having high lift is requested due to large pressure drop in system.
2. The cyclone deoiling separator is easy blocked due to coke breeze in the coke-cooling wastewater, thus the operating condition of the cyclone deoiling separator deteriorates continuously, and if serious, the production will be forced to stop.
3. In the coke-cooling hot wastewater tank, coke breeze is continuously cumulated and deposited, so the coke-cooling hot wastewater tank should be cleaned frequently, thus affecting the long-time cycle run of the process unit, and when cleaning the deposit, the released foul odor will inevitably cause secondary pollution.
4. In this utility model patent, the process for treating coke-cooling wastewater uses conventional cyclone equipments in the industry. However, these conventional cyclone equipments do not possess anti-oil emulsification effect against wastewater containing sulfur and oil. (The oil phase of the wastewater containing sulfur and oil is extremely easy to be broken and emulsified during delivery by pumping, this patent, however, pays no attention to this case.) Therefore, the separating efficiency of single stage cyclone is inevitably very low, which should be remedied by using multistage cyclones in series, thus causing the cost of the equipment double, and the problem of oil emulsification still cannot be solved. The treated water phase has much emulsified oil, which will significantly affect the efficiency of cool coking process when returning to coke tower for circulation.
Summing up, since the prior art has the above problems, up to the present, the problem of the scientific cleaning of coke-cooling wastewater cannot be solved, and the expectation of industrialization of petroleum chemical clean production cannot be met. Therefore, the art is urgent to develop a treating method for coke-cooling wastewater with low cost and good benefit, and an equipment.